Chronic Fatigue Syndrome (CFS) is a complex disease estimated to affect between 0.5%-2% of the population in the Western world. Its pathogenesis is thought to involve both inherited and environmental (including viral) components, as with other chronic inflammatory diseases such as, multiple sclerosis, rheumatoid arthritis, and atherosclerosis. Consistent with this chronic inflammatory context, CFS patients are known to have a shortened life-span and are at risk for developing lymphoma. We hypothesize that chronic inflammatory stimulation from active and recurrent infections of multiple viruses on a susceptible host genetic background leads to the pathogenesis characterized by CFS. The overall goal of this research project is to define these viral and host parameters in European and American cohorts of CFS patients that correlate with distinct disease phenotypes, including the development of mantle cell lymphoma (MCL) in a subgroup of the American cohort. In Aim 1) we will identify and confirm novel viral infections in European and American CFS patient cohorts. 1.1) we will use two complementary methods for detection of novel virus mRNA: massive parallel signature sequencing (MPSS) and a custom DNA microarray. 1.2) Quantitative polymerase chain reaction Q-PCR will be used for confirmation of virus gene expression. 1.3) immortalized cell lines will be developed to isolate virus and elucidate links between virus and host cell gene expression. In Aim 2), we will elucidate genetic factors of susceptibility and the dysregulation of the host defense system. Specifically, we will determine: 2.1) PBMC gene expression of 88 human genes previously confirmed as being differentially expressed in CFS 2.2) serum chemokine and cytokine profiles using multiplex suspension antibody arrays on a Luminex platform 2.3) HLA, KIR genotypes and whole genome SNP profiles 2.4) Defects in the type I Interferon signaling pathway. In each subaim both cohorts will be compared to normal and disease controls using specimens of serum and PBMC taken at multiple time-points from individual patients and taken from our unique and extensive sample repository. This study will provide information necessary for development of treatment and diagnostic strategies for distinct subgroups of CFS patients, and may identify novel virus associations, genetic signatures and biomarkers, which can predict the development of MCL, thus enabling use of preventive therapeutics. PUBLIC HEALTH RELEVANCE: The proposed research will provide significant insight into the disease mechanisms of Chronic Fatigue Syndrome so accurate testing and specific treatments can be developed with a goal of curing the disease and preventing life-threatening complications.